https://mandarapte.com/apple/change-upgrade-time-machine-backup-hard-disk-loosing-backups-simple-words-transfer-apple-macintosh-osx-time-machine-backups-current-backup-drive-high-storage-capacity-backup-drive/
How to change or upgrade time machine backup hard disk without loosing your old backups, In simple words how to transfer Apple Macintosh OSX Time Machine backups from a current backup drive to a new high storage capacity backup drive